Double-sear device for a forward moving barrel machine gun mounted for differential recoil



B. l. PISKATOR DOUBLE-SEAR DEVICE FOR A FORWARD MOVING BARREL MACHINE 4 Sheets-Sheet 1 Nov. 21, 1967 GUN MOUNTED FOR DIFFERENTIAL RECOIL Filed July 6, 1966 Fi l J2 LPI'SkIfiDT ATTQ iM Nov. 21, 1967 B. 1. PISKATOR 3,353,447

DOUBLE-SEAR DEVICE FOR A FORWARD MOVING BARREL MACHINE GUN MOUNTED FOR DIFFERENTIAL RECOIL Filed July 6, 1966 4 Sheets-Sheet 2 34 1 mi 30 32 I8 E 5 39 3- J.. :1 N T T3111; 7T 1 INVENTOR ATTORNEY Nov. 21, 1967 B. l. PISKATOR 3,353,447

DOUBLE-SEAR DEVICE FOR A FORWARD MO G BARREL MACHINE GUN MOUNTED FOR DIFFERENT. RECO IL Filed July 6, 1966 4 Sheets-Sheet 5 iQZQZO? 72/ INVENTOR 3 1 LPisknm ATTORNEY B. I. PISKATQR DOUBLE-SEAR DEVICE FOR A FORWARD MOVING BARREL MACHINE- 4 Sheets-Sheet 4 Nov. 21, 1967 GUN MOUNTED FOR DIFFERENTIAL RECOIL Filed July 6, 1966 I I II 36 ft .E E 66 67 W 68 k A O INVENTDR United States Patent 3,353,447 DOUBLE-SEAR DEVICE FOR A FORWARD MOV- ENG BARREL MACHINE GUN MOUNTED FOR DIFFERENTIAL RECOIL Bengt l. Piskator, Chicopee Falls, Mass, assignor to the United tates of America as represented by the Secretary of the Army Filed July 6, 1966, Ser. No. 563,654 4 Claims. (Cl. 8927) This invention relates to sears for machine guns and pertains more particularly to a double-sear device which assures that two critical conditions in the operation of the machine gun are satisfactory before the firing pin is released for discharge of the chambered cartridge.

In machine guns of the XM140 type designed for use on helicopters, which are easily changed in their flight positions by impact forces, a recoiling mass that includes the barrel and breech block is mounted on a mount for longitudinal reciprocation. Energy storing buffers are disposed between the recoiling mass and the mount so as to be energized by recoil of the recoiling mass through cartridge discharge. This energy is used to reduce the recoil force which may be transferred to the supporting vehicle, by releasing the recoiling mass so that it is moving for wardly at the time of cartridge discharge to apply the stored energy against the recoil force.

In such machine guns, too, the barrel is cycled between a forward loading and a rearward battery position and firing is effected by an operating rod, both of which are actuated by a cam drum so as to be synchronized in operation. It is obviously very important that firing is not effected unless the barrel is in battery, so that the cartridge positioned to be fired is fully chambered in the barrel, and that the recoiling mass is released from the mount and moving forwardly when the chambered cartridge is discharged, to apply the energy in the buifers against the recoil forces.

It is the principal object of this invention to provide a doublesear device which assures that both of these two critical conditions are satisfactory before the firing pin is released for discharge of the chambered cartridge.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is an elevational view of a machine gun of the XM140 type;

FIG. 2 is a view taken along line 2-2 of FIG. 1 showing the firing pin held in its cocked position;

FIG. 3 is a view similar to FIG. 2 but showing the secondary sear partially actuated to its release position by contact of the tang thereof with the cam surface on the cam slide during forward movement of the recoiling mass relative to the mount;

FIG. 4 is a view taken along line 4-4 of FIG. 3;

FIG. 5 is a view taken along line 55 of FIG. 4;

FIG. 6 is a view taken along line 6-6 of FIG. 4 and shows the primary sear actuated to its release position;

FIG. 7 is a view similar to FIGS. 2 and 3 but shows the primary sear in its release position and the firing pin in its impact position;

FIG. 8 is a view similar to FIG. 7 but shows the firing pin partially cocked by the operating rod; and

FIG. 9 is an exploded, perspective view of the doublesear device and the cocking lever.

Shown in the figures is a machine gun 12 of the XM140 type which, as disclosed in the patent application by Frederick P. Reed for Machine Gun With a Mount for Reducing the Recoil Forces Applied to the Trunnions, Ser. No. 470,942, filed July 9, 1965, now Patent No. 3,318,191 consists of a recoiling mass 14 mounted on a mount 16 Patented Nov. 21, 1967 for longitudinal reciprocation between a seared and a forward position. Recoiling mass 14 is driven to the seared position by discharge of a cartridge 18 therein against the bias of energy storing buffers 20. Recoiling mass 14 is releasably held in the seared position against the forward urging of the energy stored in buffers 20 by sears 22. Sears 22 are arranged to release recoiling mass 14 at the appropriate time before discharge of cartridge 18 so that the energy transferred from buffers 20 to the recoiling mass is applied against the recoil force produced by the discharge of the cartridge, to reduce the recoil force transmitted to mount 16.

Recoiling mass 14 includes a cam-drum 24 which is driven by electric motor means and, as described in Patent 3,241,448 to John G. Rocha for Circuitous Cam Track With Crossovers and Follower Device Therefor, is adapted to actuate barrel 26 between a forward cartridge loading position and a rearward battery position and, as described in patent application by Reed et al. for Rotary Cam Actuated Operating Rod Mechanism, Ser. No. 485,657, filed Sept. 7, 1965, now Patent No. 3,327,587 actuates operating rod 28 in forward and rearward strokes for cocking and partially releasing firing pin 30 for discharge of cartridge 18 as hereinafter described.

Firing pin 30 is mounted in breech block 32 for longitudinal displacement between a forward impact position an a rearward cocked position with a spring 34 arranged to bias the firing pin to the impact position. A cocking lever 36 is pivotally mounted on breech block 32 by means of a vertically disposed pin 38 and is connected at one end to the rear end of firing pin 30, as shown at 39, so that pivotal displacement of the cooking lever is converted to translational displacement of the firing pin, and vice versa. The outer end of cocking lever 36, noted at 40, is received by a slot 42 in operating rod 28 and such slot is terminated at the rear end by a rear wall 44 which, when in contact with bottom end 40, as shown in FIG. 8, causes cocking lever 36 to displace firing pin 30 to its cocked position during the forward stroke of the operating rod.

It is important in the operation of machine gun 12 that cartridge 18 be fired at the correct time respective to the position of barrel 26 and the release of recoiling mass 14 by sears 22. It is necessary that barrel 26 is in its battery position to assure that cartridge 18 is fully chambered therein when fired. It is also necessary that recoiling mass 14 is located between its seared and forward positions and traveling forwardly when cartridge 18 is fired to prevent the entire recoil force from being applied to mount 16 and therefrom to the transporting vehicle.

To assure that firing pin 30 is released only when the two aforementioned conditions are satisfactory, there is provided herein a double-sear device 46 which includes a primary sear 48 and a secondary sear 50 each of which is arranged as hereinafter described to releasably latch cocking lever 36 when firing pin 30 is in its cocked position. Actuation of primary sear 48 is controlled by operating rod 28 which in turn is controlled by cam-drum 24 which also controls the displacement of barrel 26, and secondary sear 50 is controlled by the position of recoiling mass 14 relative to mount 16 so that both of the critical conditions must be satisfactory for both the primary and the secondary sear to be actuated to their firing pin release positions.

To accomplish this, outer end 40 of cocking lever 36 is provided on the top side with a locking lug 52 and on the bottom side with a locking lug 54 which are engageable by secondary sear 50 and primary sear 48, respectively.

Primary sear 48 is mounted over secondary sear 50 in breech block 32 and in a common recess, as shown in FIG. 5, and each is slidingly displaceable in an essentially CD a) lateral direction between an inner release position and an outer engaging position. Springs 56 and S8 bias primary sear 48 and secondary sear 50 respectively to their engaging positions. Primary sear 48 is provided with a rearwardly extending hook 60 having an outwardly facing recess 62 and a cam surface 64 which, when contacted by locking lug 54 during forward displacement of bottom end 40 of cocking lever 36, moves the primary sear rear wardly so that the hook thereon will snap over the locking lug, which is received by the recess, to latch the cocking lever in its cocked position. Secondary sear 50 is similarly provided with a hook 66 having an outwardly facing re cess 67 and a cam surface 68 cooperating in a like manner with locking lug 52.

Primary sear 48 extends from the side of breech block 32 to form a tang 69 which is contactable with a cam surface 70 that extends inwardly and forwardly from the front end of slot 42 so that rearward displacement of operating rod 28 cams the primary sear inwardly to its release position wherein hook 60 is free of locking lug 54. The operation of operating rod 23 is so controlled by cam drum 24- in synchronization with barrel 26 that primary sear 48 is actuated to its release position when the barrel goes into its battery position.

Secondary sear 50 also extends from the side of breech 32 to form a tang 71 which is contactable with a cam slide 72 mounted on mount 16 so as to be longitudinally adjustable thereon. Cam slide 72 is provided with a cam face 74 which is contactable by tang 71 and which inclines inwardly and forwardly so that secondary sear 50 is actuatable to its release position during the forward displacement of recoiling mass 14 relative to mount 16. Cam slide 72 is adjustable on mount 16 so that any variations in the relationships of secondary sear 50. cam face 74, locking lug 52 and firing pin 30 may be compensated for to assure that the secondary sear is actuated to release firing pin 30 and cartridge 18 is discharged at the appropriate time during forward displacement of recoiling mass 14.

Operation During operation of machine gun 12, cam drum 24 is energized to cycle barrel 26 between its loading and battery positions and actuate operating rod 28 in its forward and rearward strokes. When barrel 26 is in battery position, so that cartridge 18 is fully chambered, operating rod 28 moves rearwardly to bring cam surface 70 into contact with tang 69 as shown in FIG. 6, whereby primary sear 48 is elevated to its release position wherein hook 60 is free of locking lug 54. Sears 22 are then actuated, as disclosed in the aforementioned patent application by Reed for Machine Gun With a Mount for Reducing the Recoil Forces Applied to the Trunnions, to release recoiling mass 14 from mount 16, whereby the energy stored in buffers impels the recoiling mass forwardly. During the forward displacement of recoiling mass 14 relative to mount 16 cam face 74 contacts tang 71 of secondary sear 50, as shown in FIG. 3. which is thereby actuated to its release position, freeing locking lug 52 from hook 66, as shown in FIG. 7. As cocking lever 36 is now free of both primary sear 48 and secondary sear 50 firing pin 30 is free to be impelled by spring 34 to its impact position for discharge of the chambered cartridge 18. After cartridge 18 is discharged and operating rod 28 is moved forwardly, as shown in FIG. 8, end wall 44 contacts outer end of cocking lever 36 which is thereby pivoted to displace firing pin 30 to its cocked position and locking lugs 54 and 52 are engaged respectively by primary sear 48 and secondary sear 50 to hold firing pin 30 in its cocked position.

It is readily seen from the foregoing that firing pin 30 is held retracted and cartridge 18 will not be discharged ill) 4 unless barrel 25 is in battery position and recoiling mass 14 is traveling forwardly on mount 16 so that the energy in butlers It? can be applied against the recoil force produced when the cartridge is discharged.

."tithough a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

l claim:

1. A machine gun including a mount, a recoiling mass mounted on said mount for longitudinal reciprocation between a scared and a forward position and including a breech block, a barrel actuable between a forward loading position and a rearward battery position wherein a cartridge is chambered for discharge and an operating rod acuiatable in forward and rearward strokes in synchroni- 7ation Will] the displacement of said barrel, energy storing butler means disposed between said recoiling mass and said mount so as to be energized by displacement of said recoiling mass to the seared position responsive to discharge of the cartridge in said barrel, sear means for releasably holding said recoiling mass in the seared positlOll against the forward bias of the stored energy in said butfer means. a firing pin slidingly mounted in said breech lock for displacement against the cartridge when chantbered in said barrel, a spring for impelling said firing pin forwardly from a cocked position into impact with the chambered cartridge, a cocking lever operationally disposed between said operating rod and said firing pin for converting the forward displacement of said operating rod to rearward displacement of said firing pin to the cocked position. a scar device engageable with said cocking lever when said firing pin is in the cocked position to releasably hold said firing pin therein, cooperating means on said scar device and said operating rod for partially releasing said cocking lever from said sear device when said barrel is in battery position, and cooperating cam means on said mount and said sear device for completing the release of said cocking lever therefrom when said recoiling mass is traveling forwardly from the seared to the forward position after release by said sear means.

2. The invention as defined in claim 1 wherein said cocking lever is pivotally mounted in said breech block and includes an outer end and a pair of locking lugs formed on the top and bottom sides thereof, and wherein said sear device includes a pair of sears respectively disposed for releasable engagement with a related one of said locking lugs.

3. The invention as defined in claim 2 wherein each one of said pair of sears is provided with a hook arranged to snap over the related one of said locking lugs when said charging lever is actuated to where said firing pin is di placed thereby to the cocking position for releasably holding the firing pin therein.

4. The invention as defined in claim 2 wherein said pair of sears are mounted in said breech block and include a primary sear provided with a tang contactable with a cam surface on said operating rod when said barrel is in battery position and said operating rod is moving in the rearward stroke for actuating said primary sear to a locking lug release position, and a secondary sear provided with a tang contactable with a cam plate on said mount arranged to actuate said secondary sear for release of the related one of said locking lugs during displacement of said recoiling mass from the seared to the forward position.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY. Assistant Examiner. 

1. A MACHINE GUN INCLUDING A MOUNT, A RECOILING MASS MOUNTED ON SAID MOUNT FOR LONGITUDINAL RECIPROCATION BETWEEN A SEATED AND A FORWARD POSITION AND INCLUDING A BREECH BLOCK, A BARREL ACTUABLE BETWEEN A FORWARD LOADING POSITION AND A REARWARD BATTERY POSITION WHEREIN A CARTRIDGE IS CHAMBERED FOR DISCHARGE AND AN OPERATING ROD ACTUATABLE IN FORWARD AND REARWARD STROKES IN SYNCHRONIZATION WITH THE DISPLACEMENT OF SAID BARREL, ENERGY STORING BUFFER MEANS DISPOSED BETWEEN SAID RECOILING MASS AND SAID MOUNT SO AS TO BE ENERGIZED BY DISPLACEMENT OF SAID RECOILING MASS TO THE SEARED POSITION RESPONSIVE TO DISCHARGE OF THE CARTRIDGE IN SAID BARREL, SEAR MEANS FOR RELEASABLY HOLDING SAID RECOILING MASS IN THE SEARED POSITION AGAINST THE FORWARD BIAS OF THE STORED ENERGY IN SAID BUFFER MEANS, A FIRING PIN SLIDINGLY MOUNTED IN SAID BREECH BLOCK FOR DISPLACEMENT AGAINST THE CARTRIDGE WHEN CHAMBERED IN SAID BARRERL, A SPRING FOR IMPELLING SAID FIRING PIN FORWARDLY FROM A COCKED POSITIONINTO IMPACT WITH THE CHAMBERED CARTRIDGE, A COCKING LEVER OPERATIONALLY DISPOSED BETWEEN SAID OPERATING ROD AND SAID FIRING PIN FOR CONVERTING THE FORWARD DISPLACEMENT OF SAID OPERATING ROD TO REARWARD DISPLACEMENT OF SAID FIRING PIN TO THE COCKED POSITION, A SEAR DEVICE ENGAGEABLE WITH SAID COCKING LEVER WHEN SAID FIRING PIN IS IN THE COCKED POSITION TO RELEASABLY HOLD SAID FIRING PIN THEREIN, COOPERATING MEANS ON SAID SEAR DEVICE AND SAID OPERATING ROD FOR PARTIALLY RELEASING SAID COCKING LEVER FROM SAID SEAR DEVICE WHEN SAID BARREL IS IN BATTERY POSITION, AND COOPERATING CAM MEANS SAID MOUNT AND SAID SEAR DEVICE FOR COMPLETING THE RELEASE OF SAID COCKING LEVER THEREFROM WHEN SAID RECOILING MASS IS TRAVELING FORWARDLY FROM THE SEARED TO THE FORWARD POSITION AFTER RELEASE BY SAID SEAR MEANS. 